Diffusion transfer system



United States Patent m 3,396,018 DIFFUSION TRANSFER SYSTEM Dorothy J. Beavers and Guernsey K. Edmonds, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed May 17, 1963, Ser. No. 281,357 7 Claims. (Cl. 96-29) This invention concerns a developer for use in a photographic diffusion transfer system, more particularly a developer containing nuclei and the process of using such a developer.

The diffusion transfer process is well known in the photographic art as a method for producing fairly rapidly photographic prints which require a minimum of after treatment such as fixing and the like. The silver halide emulsion is exposed to light and developed with a silver halide developer having therein a silver halide solvent and contacted against the receiving sheet. The receiving sheet contains nuclei which form sites for physical development of the silver halide which diffuses imagewise from the silver halide emulsion to the receiving sheet.

In an adaption of this process, a highly viscous developer is used which contains nuclei in the developer instead of on the surface of the receiving sheet. However, in the known processes, a viscosity of over 1,000 centipoises (cps.) is required in the transfer which will form useful images only on smooth surfaces such as baryta-coated paper, film or the like. This has somewhat limited the usefulness of the diffusion transfer process, since it has been desirable to transfer an image 'by this method to various types of substrates such as metal, cloth, leather and the like which provide irregular surfaces. Moreover, some of the developer is retained on the final print and processing apparatus producing undesirable stain unless subsequently removed by washing.

We have found a method of incorporating the nuclei in the developer and overcoating a silver halide emulsion so that good chemical transfer images can be formed on irregular surfaces as well as on smooth surfaces.

One object of this invention is to provide a nuclei containing developer for use in the diffusion transfer system. Another object is to provide a diffusion transfer method of forming images on irregular surfaces. A further object is to provide a silver halide emulsion for use in the solvent transfer system producing improved results when contacted against a receiving support. A still further object is to provide a solvent transfer process using an overcoated silver halide emulsion and a nuclei containing developer.

The above objects are obtained by preparing a silver halide emulsion in a well known manner and then overcoating this light-sensitive silver halide emulsion with an overcoating of an alkali-permeable polysaccharide, e.g. carboxymethyl cellulose or hydroxyethyl cellulose. This coating is relatively thin having a preferred coverage of about 0.1 gram per square foot. However, a useful range may be from .03 to 1.0 gram per square foot. The developer solution may contain one of the known silver halide developers and a silver halide solvent but also contains nuclei. The preferred viscosity of this developer solution containing nuclei is between 2.5 and 250 centipoises, although a viscosity range between 1.0 and 300 centipoises is useful in many applications.

Although our preferred nuclei is zinc sulfide, it will be appreciated that other typical nucleating or silver precipitating agents which are known in the solvent transfer system may be used such as particles of silver, other metal sulfides, metal selenides, silver proteinate, etc. These nucleating agents include Carey Lea silver and the colloidal sulfides and selenides of the metals of Groups Ib, IIb, IVb

3,396,018 Patented Aug. 6, 1968 and VIII of the Periodic Table, e.g. zinc, cadmium, nickel, etc. Mixed nuclei may also be used. These nuclei parti les preferably have an average diameter of about 25 to 2,500 A.

The silver halides useful in this process may comprise any of the conventional gelatino silver halide emulsions, e.g., gelatino-silver chloride, -chlorobromide, -chl0r0- iodide, -chlorobromoiodide, -bromide, and -bromoiodide emulsions. The emulsions for use in the invention include emulsions having a silver halide carrier other than gelatin, for example, collodion, albumin, synthetic resins and the like. These emulsions can be coated in the usual manner on a suitable support, e.g., glass, cellulose nitrate film, cellulose ester film, paper, 01' metal, etc.

The silver halide developing solution used for initiating development of the exposed sensitive element is not especially critical. It can be of the conventional type used for developed films or papers with the exception that a silver halide solvent such as sodium thiosulfate, sodium thiocyanate or ammonia is present in the quantity required to form a soluble silver complex which diffuses imagewise to the receiving support. Silver halide developing agents useful in the developing solution include hydroquinone, monomethyl-p-aminophenol sulfate, aminophenols, halogenated hydroquinones, toluenequinone, p-hydroxy phenyl, aminoacetic acid, 3-pyrazolidone developing agents such as l-phenyl-3-pyrazolidone and mixtures of these developing agents. Useful developer compositions containing combinations of 3-pyrazolidone silver halide developing agents with weak developing agents such as ascorbic acid are disclosed in US. Patents 2,688,549, 2,691,589, 2,688,548, 2,685,515, 2,685,516 and 2,751,300.

It will be appreciated that common emulsion addenda such as chemical and spectral sensitizing agents which are known in the art can be added to the photographic emulsions and also that diffusion transfer toners known in the art can be incorporated in the developer. Typical toners are shown in the following patents:

Great Britain 861,255 Great Britain 868,243 France 1,192,179

In our preferred embodiment, carboxymethyl cellulose is coated in an amount of 0.10 gram per square foot over N. When zinc sulfide is the nuclei used, we prefer a 00012 N solution or 0.06 gram per liter.

Although our preferred overcoating material is carboxymethyl cellulose, other alkali-permeable coating materials may be used, particularly polysaccharides such as water soluble cellulosic polymers and including hydroxyethyl cellulose and the like.

It will also be appreciated that our process can be used with absorbent surfaces as well as those which are considered relatively non-absorbent. For example, inexpensive paper sheets may be used as well as those which have thereon a polymeric coating to render them glossy, those which are baryta or clay coated and the like. This process may also be used for transfers to cloth, wood, brick and other irregular surfaces.

The photographic process disclosed herein is particularly applicable to chemical transfer multicopy systems wherein successive copies are made from a single exposed negative .by the diffusion or chemical transfer system. In the past, this system has relied upon nuclei coated on the surface of the receiving sheets requiring a relatively expensive receiving sheet, whereas these sheets used in our process could be of any composition, without a special nuclei coating, the nuclei employed in the process being contained in the developer solution. When used in a multicopy process, the negative does not need to be overcoated with a polysaccharide overcoating.

Since one of the advantages of 0111' process is that prints can be made on metal surfaces, this process is particularly applicable to the preparation of lithographic plates, avoiding the necessity that the plate be specially prepared or nucleated. Using the nuclei containing developer, the image is transferred directly to the lithographic plate which may be an aluminum or similar metal plate and then swabbed with a mercapto compound to convert the silver image to a silver sulfide image which is ink receptive. The lithographic plate can be any clean metallic surface preferably free from any metal or metal salts, which will react with the mercapto compound. Although it is preferred to swab the print with a mercapto compound, it will be appreciated that any of the known swabbing compounds used for this purpose may be used such as xanthates, etc.

A further adaptation of our process involves the use of a photographic emulsion that has been .overcoated with a pigmented layer such as titanium dioxide in an alkalipermeable colloid binder. In a preferred structure, the silver halide emulsion is overcoated with a gelatino titanium dioxide layer. When the emulsion is exposed and developed using the nuclei containing developer, a direct positive silver image is formed on the surface of the titanium dioxide layer without requiring the use of a separate nucleated receiving sheet which must then be stripped away from the negative element. A layer of gelatin may be coated over the titanium dioxide layer if desirable but is not necessary.

The following examples are intended to illustrate our invention but not to limit it in any way.

EXAMPLE I To a kettle at 40 C., add 2880 grams 25 percent gelatin solution, 270 ml. water, a solution of 318 grams sodium thiosulfate (SH O) in 960 ml. H 0, 15 grams sodium sulfite and 12 ml. of gel preservative. Dissolve and add 120 ml. of 1.0 N sodium sulfide and stir 3 minutes. A solution of 125 ml. zinc nitrate (1.0 N) is diluted to 1580 ml. with water and this solution is added to the kettle. In 5 minutes at 40 C. this nuclei solution was then used in the following formulation.

4.. oper formulation with various concentrations of nuclei and contacted while still wet against a baryta-coated paper sheet for seconds. The developer composition was varied as shown in Table I and repeated using the 5 same silver halide emulsion. The viscosity of a developer formulation wherein 60 'g./liter of .02 N ZnS nuclei in 12% gel was utilized was 2.6 cps. "at 25 C. i 'i TABLE I Resultant (N) g./1. of D Maximum 10 Developer Number N ormulity of ZnS Baryta Coated ZnS Developers nuclei Paper Stock 0.0 0.0 100. 0.00002 N 0.0010 0.26 0.0001 N 0. 0050 0.28 0.0002 N 0. 0100 0. 19 0. 0004 N 0.0200 0. 83 0 0008 N 0. 0400 1.04 0. 0016 N 0.0800 1. 0. 0032 N 0. 1600 0. 70 0. 0016 N" 0. 0800 0 62 0020 N 0. 1000 1 20 0.04 N ZnS in 1% gelatin utilized in these developers.

2 At concentrations of 0.0004 N zinc sulfide or 0.02 gram of zinc sulfide per liter the density approaches acceptability. At concentrations of 0.0008 N or 0.0016 N zinc sulfide the densities get higher and approach a maximum density at around .002 N zinc sulfide. Higher concentrations (0.003 N) and nuclei appear to cause some sludging and high background density although the image density is still good. Therefore, the preferred density for obtaining a high quality point with regard to maximum density and background is between 0.0008 N and 0.0016 N zinc sulfide.

EXAMPLE II The following results were obtained using the process of Example I with various paper stocks as receiver sheets on both sides. The developer tested was 0.0016 N ZnS (No. v11

The process of Example I was used with negatives having an ovecoat of CMC (carboxymethyl cellulose) on the negative compared to negatives without an overcoat. The following results shown the improvement obtained.

OMC Overcoat 011 Negative Positive Developer Din. Sticking Mottle None, 0.1 gJft. 22.51b./1,000 It. paper stock Developer I (no nuclei)- 818% igfig ggg None, 0.1 g./ft. Baryta coated 271b./1,000tt. paper stock Developer I (no nuclei) g: g 20 EQE gg g N one, 0.1 glft. Baryta coated 271b./1,000 ft. paper stock. Developer X (0.0020 N ZnS) :35:: ggf

Basic C.T. developer formulation: G. EXAMPLE IV 6O 1-phenyl-3-pyrazohdone 1 Hydroquinone 18 Developer formulation variations in which the l-phen- Net- 80 75 yl-3-pyrazolidone, sodium thiosulfate concentration, and NaOH 11.2 cold toner have all been increased by small amounts KBr 1.0 have resulting in increasing the maximum density to a Ethylenediamine tetraacetic acid sodium salt 1.0 Dmax, of 1.4 with 27 lb./ 1000 ft? baryta-coated stock, Sodium thiosulfate pentahydrate 6.0 1.32 with 201/ lb./ 1000 ft. lbaryta coated stock and 5-ethyl-5-methyl-4-th1ohydantoin 0.4 around 1.10 for 22 /2 lb./ 1000 ft. stock. An anti-stained,

.02 N ZnS nuclei in 12% gel, 5.3% sodium thiosulfate (O to 100 g. of nuclei). Water to one liter.

A gelatino silver chloride emulsion coated on a support was overcoated with a 0.10 gram per square foot of carboxymethyl cellulose. After exposing the emulsion to an image, it was immersed in the above basic C.T. develtu b-sized nucleated sheet when processed in Developer I containing no nuclei, had a density similar to that obtained with a plain paper base receiver processed in a nuclei-containing developer. Also, a normal coated nucleicontaining receiver sheet passed through nuclei-containing developers such as Developers V or VI exhibited good density with no increase in background.

EXAMPLE v In Example II, baryta-coated antistained stocks and nonba'ryta coated stocks were listed as receivers. Water finish stock, 20 lbs. partially acetylated stock and stock containing phthalic acid-gel as antistain addenda give good to excellent prints in the nuclei developer llsted in Example I.

Two-sided high quality prints were made from standard typing paper. A good print is obtained on cheap balance paper used for weighing chemicals. Light mounting and heavy mounting cardboard produce excellent doublesided prints in these nuclei developers with overcoated negatives. A standard C.T. processing machine such as the Apeco Director or A. B. Dick processing units are used for making prints although a simple developer tray with a squeegee gives equally good results.

EXAMPLE VI Miscellaneous C.T. receivers used with overcoated negatives and nuclei developers In the nuclei developer described in Example I, the overcoated negative was processed for four seconds at room temperature, squeegeed, and then placed in contact with several mateials for 20 seconds then stripped. An excellent high density uniform transfer was made to a dry block of wood. A sheet of dry polyethylene and a sheet of leather gave an excellent black image which upon drying was reasonably permanent. Transfers were made on subbed and non-subbed glass plates as Well as transparent film base. Corrugated cardboard and cloth gave good images. Brick and stone also gave fair images. Good transfer were made to aluminum foil and aluminum metal. A good transfer was also made to human skin. No material has been found which the negative will not transfer an image to if the overcoated negative is process-ed in these nuclei developer-s.

EXAMPLE VII With silver sulfide, less nuclei are needed per liter of developer than with zinc sulfide. Silver sulfide gives a higher image density with a warmer tone and somewhat more background density than zinc sulfide. Examples of developers containing nickel and silver sulfide are given below.

A nickel sulfide nuclei developer (0.034 'g./l.): G.

Ethylenediamine tetraacetic acid sodium salt 1.0 l-phenyl-3-pyrazolidone 1.0 Hydroquinone 18.0 Na SO 75.0 NaOH 11.2

KBr 1.0 Sodium thiosulfate pentahydrate 6.0 5-ethyl-5=methyl-4-thiohydantoin 0.4

Dissolve above addenda in 800 ml. water. Take 100 g. of 00075 N nickel sulfide prepared in 2% gel and melt. Add to 800 ml. water slowly with good stirring and adjust volume to one liter. Densities and background of prints were higher with nickel sulfide developers than with zinc sulfide nuclei developers.

A silver sulfide developer was prepared as above except that 125 g. of 0.005 N silver sulfide in 2% gel was used in the nuclei developer. Good results were obtained.

A Carey Lea silver nuclei developer was prepared as above except that 0.5 g./liter of Carey Lea silver in gelatin was added. Prints of medium density and higher background were obtained. The prints did not have as high quality as obtained With metal sulfide nuclei developers.

6 EXAMPLE VIII The developer described in Example I was prepared with 60 g./l. of ZnS (0.02 N) in 12% gel. The developer has shown good stability for more than eight months when stored in a closed container. The prints obtained in this developer with .baryta-coated receivers. have densities of 1.1 to 1.2 with a slight increase, in print background. Rough surfaced paper bases give prints of lower density (1.0 to 0.60) after fourth months natural aging;

One, liter of theabove nuclei developer with 10 g./l. sodium thiosulfate was tested for exhaustion with overcoated C.T. negative and baryta-coated receiver. Excellent high density prints of good brack ground were obtained for 50 prints, the next 20 prints had a light background density. After prints the background density was about 0.2 although the maximum density had not decreased. When an antisludging agent was incorporated in the developer formulation it was possible to obtain over prints of good quality before the background density began to increase.

Nuclei were prepared in colloids other than gelatin such as acrylic acid-ethylacrylate (2080) copolymer, carboxymethyl cellulose, and dextrin. The nuceli developers prepared from these collodids preferably contain 2 or 4 g. of colloid per liter of developer.

ZnS nuclei were prepared in 5% gelatin and these developers gave excellent results. The addition of small quantities of gelatin to the nuclei developers did not change their viscosity noticeably.

Cps. C.T. developer I, no gelatin added 2.5 ZnS nuceli developers, 3 g./l. gelatin 2.5 ZnS nuclei developer, 7.2 g./l. gelatin 2.6

EXAMPLE IX C.T. nuclei-developer prepared from phenidone ascorbic acid Dilute above developer components with 800 ml. of water. Dissolve 60 g.-0.02 N ZnS in 12% gel in 100 ml. H O. Add slowly to developer and adjust volume to one liter.

The above developer Was tested with an overcoated negative with baryta coated and uncoated paper base receivers. The resultant prints were of fair quality.

EXAMPLE X C.T. nuclei developer prepared from 1-phenyl-3- pyrazolidone and p-methylaminophenol sulfate 1-phenyl-3-pyrazolidone and p-methylaminophenol sulfate: G. 1-phenyl-3-p-yrazolidone 1.0 p-Methylaminophenol sulfate 12.0 Na SO 75.0 NaOH 1 1.2

KBr "n Y 1.0. Ethylenediamine tetraacetic acid, sodium salt 1.0 Sodium thiosulfate pentahydrate 10.0 Cold toner 0.5

Add water to make 800 ml. of solution. Dissolve 60 g. of 0.02 N ZnS in 12% gel in 100 ml. H O. Add slowly to developer solution. Adjust water to one liter total volume. Viscosity 2.6 cps. at 25 C.

The above developer was tested with an overcoated C.T. negative, and baryta coated paper bases. Excellent high density prints were obtained. Excellent densities were-obtained with the rougher surfaced paper base.

Solution BAdd 134 ml. of water ito 266 g. of 3% hydroxyethyl cellulose (HEC, type WP-40, low viscosity). Heat to 40 C. with stirring/Add 60. g.

I r f 0.02 N ZnS nuclei in 12% gelatin in small pieces nucleldvclopel' wlth hydfoqulnone-Eloni 5 and dissolve in the warm HEC. Add 40 ml. sur- Hydfoqulnolle factant p-tert.-octyl phenoxyethoxy ethyl sodium sul- E (gemflhylammophenol sulfate)v fonate 0.07 g./ml.) and dilute to 500 ml.

: a I. b I I Slowly add Solution A to SOIUIIOHB and stir until a uniform mixture results. Viscosity=21 cps.

Ethylenediamine tetraacetic acid, sodium salt 1.0 10 Developer C: Modified Developer B with 0.43% HEC Sodiumthiosulfate pentahydrate 10.0 (type 250H, high viscosity) and containing 1.1 times Cold toner, 0.2 to 0.5 g. water to 800 ml. as much developer componentsfAlso 143 g. of 0.02 N Dissolve 60 g. of 0.02 N ZnS prepared in 12% gel 6 5 g 5 33 a i i gg 60 in 100 ml. water. Slowly add the nuclei to the developer 15 0 m 0 ga a Lscosl YT with good stirring. Adjust volume to one liter. Viscosity Developer D: 2.6 cps. at 25 C. Solution A-As in Developer A but total volume low- The above hydroquinone-Elon developer was tested ered to 500 ml. and no nuclei present. with an overcoated C.T. negative and baryta-coated and Solution BDissolve 6.5 gins. HEC (type 250H, high uncoated paper bases. Excellent high density prints with viscosity) in 440 ml. of water with stirring at 40 C. no background were obtained with the baryta-coated Slowly add 60 g. of 0.02 N ZnS nuclei in 12% stocks. Non-baryta coated stock gave a print of medium gelatin in small pieces and dissolve in the warm density' and excellent background. HEC. Adjust volume to one liter.

EXAMPLE XII Slowly add Solution A to Solution B and stir until a Several C.T. nuclei developers were prepared Without umform mlxture results vlscosltyzwo. any toner present in the developer. Addition of a small Developer E: As in Developer D but 7.5 gms. of HEC amount of ZnS nuclei, e.g., 0.001 g./l. immediately in- (type 250H, high viscosity) were utilized in Solution creased the Dmax. of a print made on baryta-coated stock B. Viscosity=420 cps. from to 2 There plateau q The following table illustrates the effect of the various ggg f 6 gi i E; f i g $2 th above developers when used in combination with negative t Q 9 d n 1 nuc .i 6 elements containing no overcoat or containing either a amoun i i Opus b hydroxyethyl cellulose (HEC) or carboxymethylcellulose X Y:. 1 one Image: 0 f g gg z (CMC) overcoat. The developers were placed between @1151 th arger amqun s o 1 no the negative and positive sheets and the two sheets fed e lmzgge g f a co er t 5 1 through two metal rollers with a slit width of 0.002" and d out a .3? oxtymet Ce u ose i f e a travel speed of three or processed in an Apeco Direc- QZ'; g i out 23 .glve poor g ensl g tor C.T. machine (except for cloth). The cloth'was satug" rown m0 6 Images an 1g ac groun 40 rated with developer and squeegeed in contact with the names EXAMPLE XIII negative which had been immersed in developer. The two sheets were stripped apart after five seconds or more. The following developers were prepared to compare The following results were obtained.

TABLE II Viscosity, Negative Receiver Receiver Sticking Proponsity' cps. (25 C.) (O7ercgat): Support Surface Dmnx. Image Quality. (Negative to Receiver) g. sq. r.

Developer:

A 2.5 None Paper-.... Smooth-.. Low Uniform. Very slight.

2.5 .-...do.... do.... Irregular- Low... Streaky- None. 2. 5 .....do Cloth ..do Very low--.. Uniform Do. 7 2. 5 0.1 g. CMC Paper..... Smooth.-.- Very high ..do None, excellent stripping. 2.5 0 1g. HEC.- do ..do None. 2. 5 0.1 g. ..do-.. None, excellent stripping. 2.5 0.1 g. .....do None. 2.5 0.1g. do 21 o Mottled, streaky.- 21 g 21 ..do ..do Do. 175 ..do... Mottled image High. 175 .do Sl. mottle, uniform None. 370 Mottled, streaky 370 ..do 370 erylo\v.. 370 370 HEC do....- Irregular... Low o None. 370 Cloth ..do High. 420 Paper..... Smooth-... L0w.. 420 -do-.... Irregular-.. Lcw-. 420 .-...do 0 th ..do Very low St y 420 0.1g. HEG Paper..... Sn1ooth--.. High.. Mottled, streaky 420 0.1 g. HEC ..do..... Irregular.-. Low ..do None. 420 0 1g EEC Cloth ..do High Uniform D0.

the efiect of difierent developer viscosity levels in our invention. Viscosity measurements were made at 25 C. by using a Brookfield LVT-viscometer #1 spindle. Developer A: Basic C. T. developer of Example I utilizing gms. of 0.02 N ZnS nuclei in 12% gelatin. Viscosity=2.5 centipoises (cps). Developer B:

Solution A-As in Developer A but total volume lowered to 500 ml. and no nuclei present.

' From the above Table II it is seen that the higher viscosity 300), nucleated developers exhibit a. high sticking propensity and poor image quality when utilized with smooth surfaced receiver sheets. It is also apparent that these higher viscosity developers will not work satisfactorily with the irregular surfaced paper receivers wherein, even when utilized with an overcoated negative element, they tend to exhibit low density, mottled images and high background density. In addition, dilficulty was encoun- EXAMPLE XIV Study of negative overcoats When nuclei developers are used with paper base receivers, it is desirable that the negative used for the chemical transfer have an overcoat.

Excellent results are obtained with varying amounts (per square foot) and types of carboxymethyl cellulose, sodium salt, such as types 7E, 7G, 7AP, 7LP, etc., obtained from Hercules Chemical Company, and types S- 75L, P-75L, S-75LM and S-75LX obtained from the Du Pont Company.

Excellent results are obtained with hydroxyethyl cellulose derivatives. Examples of this type of overcoat are obtained with varying amounts of Union Carbide Chemical Companys HEC types WP03, WP-09 and WP -40. Other negative overcoats include 0.1-.2 g./ft. starch and 0.2 g./ft. of sodium alginate. The maximum densities obtained with these overcoats was high and no mottle was obtained with baryta-coated stocks. With rough surfaced antistain paper bases, starch and alginate negative overcoats gave good uniform medium densit prints with no background.

The amount and range of nuclei necessary to give good densities may vary in the case of one nuclei and another. For example, only one-third or one-half as many silver sulfide nuclei are necessary to get the same density as with Zinc sulfide. Further, nuclei prepared in a different manner than illustrated in Example I may not be as active, and less active nuclei will require a higher concentration of nuclei.

It will be appreciated that the silver halide solvent may be incorporated in a layer under the silver halide emulsion instead of in the developer solution or that the nuclei containing developer may contain all or part of the silver halide solvent needed. If desired, all or part of the silver halide solvent and a cold toner may be incorporated into the paper support.

EXAMPLE XV A fine-grained silver chloride emulsion was coated at 45 mg. Ag/ft. on regular paper base. Over the emulsion was coated a layer of titanium dioxide at about 2.0 g./ft. which was dispersed in. about 0.3 g./ft. gelatin. This coating was then exposed by contact printing with a positive transparent original on the Brumberger B printer for 40". Exposed strips of this integral chemical transfer element were developed for 20, and 4" (Apeco) to determine how fast the emulsion developed. The developer Dissolve above in 800 ml. water.

To 60.0 g. of 0.02 N ZnS nuclei prepared in 12% gel add 100 ml. water and dissolve. Slowly add the nuclei to the developer components and adjust the volume to one liter. Viscosity 2(6 cps.

The fine-grained silver chloride emulsion developed in ten seconds and within thirty seconds the positive image began appearing on the surface of the titanium dioxide layer. After a minute, maximum print density was reached. The print was squeegeed directly after 10-15 seconds development or after the complete appearance of the image.

With the fine-grained silver chloride emulsion it was possible to carry out the complete process under subdued tungsten lights. The image density was a medium black with a D of 0.80 or more and a white background.

EXAMPLE XVI The emulsion-titanium dioxide coating described in Example XV was processed in a nickel sulfide nuclei developer as described in Example 1. Image densities were gray-black with a somewhat higher background density than obtained with zinc sulfide nuclei developers. With silver sulfide nuclei developers the images obtained were warm toned black images with a somewhat higher background density than obtained with ZnS nuclei developers.

EXAMPLE XVII A medium-grained silver chlorobromide emulsion with a high cadmium content was coated as a negative emulsion layer at 22 mg. Ag/ft. with 0.24 g./ft. gelatin. Over this emulsion was coated a layer of titanium dioxide, 2.0 g./ft. in about 0.3 g./ft. gelatin. A medium-grained silver chlorobromide emulsion of higher speed than the fine-grained silver chloride emulsion utilized in the previous example was exposed for /2" at 75 v. in the Brumberger B printer. The exposed negatives were developed for 20 seconds under safelites, then the negative squeegeed and the developed pint allowed to stand while the silver halide migrated to the top layer. After 2 minutes time the image had reached a maximum density and the lights were turned on. After one minute the image seemed unaffected by the presence of room lights. The whole process could not be carried out under room lights as with the finer-grained chloride emulsion, because the higher speed emulsion fogged and no positive image appeared. Medium-gray densities of the order of 0.7 were obtained with the medium-grained higher speed silver chlorobromide emulsion.

EXAMPLE XVIII A nuclei developer was prepared in the following manner.

NiS nuclei developer: G. 1-phenyl-3-pyrazolidone 1.0 Hydroquinone 18.0 Na SO 75.0 NaOH 11.2 KBr 1.0 Ethylenediamine tetraacetic acid, sodium salt 1.0. Sodium thiosulfate pentahydrate 6.0

5-ethyl-S-methyl-4-thiohydantoin 0.4 Waterto make 800 ml.

Disperse g. of 0.0075 N NiS in 2% gel. Add slowly to the developer components and dilute to one liter.

The multicopy negative used was a medium-grained silver chloride emulsion which was not overcoated with carboxymethyl cellulose. The exposed emulsion with EXAMPLE XX A medium-grained silver chlorobromide emulsion without an overcoat was processed in the CT. nickel sulfide developer with paper base as described in Example XIX. Three good copies with a brown image tone were obtained from one negative.

EXAMPLE XXI A fine-grained silver chloride emulsion containing a carboxymethyl cellulose overcoat and one containing a hydroxyethyl cellulose overcoat were processed in the CT. nickel sulfide developer as described in Example XIX. Two good copies were obtained from each of the negatives.

EXAMPLE XXII A developer was prepared in the following manner with no toning agent, and less silver solvent, e.g. sodium thiosulfate, than in the developer of Example XIX.

ZnS nuclei developer: G. 1-phenyl-3-pyrazolidone 1.0 Hydroquinone 18.0 N21280:; NaOH 11.2

KBr 10 Ethylenediamine tetraacetic acid, sodium salt 1 Sodium thiosulfate pentahydrate Water to make 800 ml.

Disperse 60 g. 0.02 N ZnS nuclei in 100 ml. H O. Add slowly to developer components and adjust volume to one liter.

The negative was a fine-grained sliver chloride emulsion (about 90 mg. Ag) overcoated with a carboxymethyl cellulose layer. Baryta-coated 27 lb./1000 ft. paper stock receivers were processed in the nuclei developer as described in Example XIX. Two fair copies were obtained from one negative. When the fine-grained silver chloride emulsion was replaced with a larger grain silver chlorobromide emulsion, three good copies were obtained.

EXAMPLE XXIII G, 1-phenyl-3-pyrazolidone 1.0 Hydroquinone 18.0 Sodium sufite 75.0 Sodium hydroxide 11.2 Potassium bromide 1.0 Ethylenediamine tetraacetic acid, sodium salt 1.0 Sodium thiosulfate pentahydrate 10.0 5-ethyl-5-methyl-4-thiohydantoin 0.4

The above addenda were dissolved in 800 ml. water at room temperature. A solution of 60.0 g. of 0.02 N zinc sulfide nuclei prepared in 12% gelatin was dissolved in ml. of water and slowly added to the developer solution with good stirring at room temperature. The final volume was adjusted to one liter. 1 i t The plate was used for aprinting run. The ink receptivity and image durability of the plate prepared with nuclei developers was very good.

EXAMPLE XXIV The same procedure is followed as in Example XXIII using a cheap aluminized untreated paper. With the smooth surfaced paper, good ink receptivity and image quality are obtained. 1

EXAMPLE XXV A carboxymethyl cellulose overcoated silver chloride emulsion was exposed in the Apeco Director machine. It was then placed in contact with an aluminum sheet which had been rinsed in dilute acid, The negative and sheet were immersed in a nuclei developer solution for five seconds, squeegeed in contiguous relationship, and left in contact for twenty seconds. The sheets were stripped apart leaving a positive image on the aluminum sheet. The plate was dried, then swabbed with Kodak Offset Fix #3 containing a mercapto compound.

The lithographic plate was tested for its printing ability. About 100 good copies were obtained from the plate.

As is customary with lithographic plates formed by the chemical transfer method, the silver image must be swabbed with sulfur compounds such as mercaptans, xanthates, etc., to make them ink receptive.

This process can also be used to provide add-ons for microfilm. Many data are recorded on microfilm to conserve space, but there has been some diificulty in adding new data or changing data already recorded without actually splicing a new section of microfilm into the roll to replace the section containing the. new data. By means of our process, the new data can be photographed on a suitable emulsion and a positive image transferred to the microfilm. Blank spaces on the microfilm can be provided to permit these add-ons.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A process for obtaining an image by the silver halide diffusion transfer method on an irregular surface comprising developing an exposed silver halide emulsion having thereon a substantially dried down overcoat of an alkali permeable polysaccharide with a. silver halide developer solution having a viscosity of 1.0 to 300 centipoises containing silver precipitating nuclei and a silver halide solvent, and contacting the said polysaccharide while still wet with the said developer against a receiving support.

2. A process of claim 1 wherein the said polysaccharide is carboxymethyl cellulose.

3. A process of claim 1 wherein the said polysaccharide is hydroxyethyl cellulose.

4. A process of claim 1 wherein the said developer contains zinc sulfide.

5. A process of claim 1 wherein the said polysaccharide layer is contacted against a metallic plate to make a photographic printing plate.

6. A process of claim 1 wherein the said polysaccharide layer is contacted against an aluminum plate to make a photographic printing plate. v

7. A process of claim 1 wherein the said polysaccharide 13 14 layer is contacted against a film support to add an image 2,944,894 7/ 1960 Land 96-29 thereon. 2,984,565 5/1961 Moise 9629 References Cited 3,186,842 6/ 1965 DeH-aes 96-29 UNITED STATES PATENTS 5 NORMAN G. TORCHIN, Primary Examiner. 2500421 3/1950 Land GERRY COHN, Assistant Examiner.

2,662,822 12/1953 Land 96-29 

1. A PROCESS FOR OBTAINING AN IMAGE BY THE SILVER HALIDE DIFFUSION TRANSFER METHOD ON AN IRREGULAR SURFACE COMPRISING DEVELOPING AN EXPOSED SILVER HALIDE EMULSION HAVING THEREON A SUBSTANTIALLY DRIED DOWN OVERCOAT OF AN ALKALI PERMEABLE POLYSACCHARIDE WITH A SILVER HALIDE DEVELOPER SOLUTION HVING A VISCOSITY OF 1.0 TO 300 CENTIPOISES CONTAING A SILVER PRECIPITATING NUCLEI AND A SILVER HALIDE SOLVENT, AND CONTACTING THE SAID POLYSACCHARIDE WHILE STILL WET WITH THE SAID DEVELOPER AGAINST A RECEIVING SUPPORT. 